[PATCH] ArmPkg: Fix double GIC EIOR write per interrupt

[evan.lloyd@arm.com]

From: Alexei <Alexei.Fedorov@arm.com>

This commit fixes a bug in the GIC v2 and v3 drivers where the GICC_EOIR
(End Of Interrupt Register) is written twice for a single interrupt.
GicV(2|3)IrqInterruptHandler() calls the Interrupt Handler and then
GicV(2|3)EndOfInterrupt() on exit:

 InterruptHandler = gRegisteredInterruptHandlers[GicInterrupt];
 if (InterruptHandler != NULL) {
   // Call the registered interrupt handler.
   InterruptHandler (GicInterrupt, SystemContext);
 } else {
   DEBUG ((EFI_D_ERROR, "Spurious GIC interrupt: 0x%x\n", GicInterrupt));
 }

 GicV2EndOfInterrupt (&gHardwareInterruptV2Protocol, GicInterrupt);

, although gInterrupt->EndOfInterrupt() has already been called by
InterruptHandler().

The fix moves the EndOfInterrupt() call inside the else case for
unregistered/spurious interrupts.  This removes a potential race
condition that might have lost interrupts.

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Alexei Fedorov <alexei.fedorov@arm.com>
Signed-off-by: Evan Lloyd <evan.lloyd@arm.com>
---

Code is available at:
https://github.com/EvanLloyd/tianocore/tree/EOIR_v1

 ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c | 5 ++---
 ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c | 5 ++---
 2 files changed, 4 insertions(+), 6 deletions(-)

diff --git a/ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c b/ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c
index 036eb5cd6bf6845dd2b03b62c933c1dedaef7251..34d4be3867647e0fdad7356c949af8cd3ede7164 100644
--- a/ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c
+++ b/ArmPkg/Drivers/ArmGic/GicV2/ArmGicV2Dxe.c
@@ -2,7 +2,7 @@
 
 Copyright (c) 2009, Hewlett-Packard Company. All rights reserved.<BR>
 Portions copyright (c) 2010, Apple Inc. All rights reserved.<BR>
-Portions copyright (c) 2011-2015, ARM Ltd. All rights reserved.<BR>
+Portions copyright (c) 2011-2016, ARM Ltd. All rights reserved.<BR>
 
 This program and the accompanying materials
 are licensed and made available under the terms and conditions of the BSD License
@@ -178,9 +178,8 @@ GicV2IrqInterruptHandler (
     InterruptHandler (GicInterrupt, SystemContext);
   } else {
     DEBUG ((EFI_D_ERROR, "Spurious GIC interrupt: 0x%x\n", GicInterrupt));
+    GicV2EndOfInterrupt (&gHardwareInterruptV2Protocol, GicInterrupt);
   }
-
-  GicV2EndOfInterrupt (&gHardwareInterruptV2Protocol, GicInterrupt);
 }
 
 //
diff --git a/ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c b/ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c
index 106c669fcb8777dfaad609c0ce9f5b572727a3ff..983936f3738a74bb5d5e08e012973df240958a8b 100644
--- a/ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c
+++ b/ArmPkg/Drivers/ArmGic/GicV3/ArmGicV3Dxe.c
@@ -1,6 +1,6 @@
 /** @file
 *
-*  Copyright (c) 2011-2015, ARM Limited. All rights reserved.
+*  Copyright (c) 2011-2016, ARM Limited. All rights reserved.
 *
 *  This program and the accompanying materials
 *  are licensed and made available under the terms and conditions of the BSD License
@@ -169,9 +169,8 @@ GicV3IrqInterruptHandler (
     InterruptHandler (GicInterrupt, SystemContext);
   } else {
     DEBUG ((EFI_D_ERROR, "Spurious GIC interrupt: 0x%x\n", GicInterrupt));
+    GicV3EndOfInterrupt (&gHardwareInterruptV3Protocol, GicInterrupt);
   }
-
-  GicV3EndOfInterrupt (&gHardwareInterruptV3Protocol, GicInterrupt);
 }
 
 //
-- 
Guid("CE165669-3EF3-493F-B85D-6190EE5B9759")